Window doesn't show up

When a window doesn't have a size allocation on construction, it will never show up. You can solve this by wrapping the children in a box and forcing the box to have some size. For example when the window's direct child is a revealer that starts off with reveal_child: false

Widget.Window({
  child: Widget.Box({
    css: "padding: 1px;",
    child: Widget.Revealer(),
  }),
});
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Custom svg symbolic icons

Put svgs in a directory, named <icon-name>-symbolic.svg and use App.addIcons or icons option in exported object

// config.js
App.addIcons(`${App.configDir}/assets`);

Widget.Icon({
  icon: "custom-symbolic", // custom-symbolic.svg
  css: "color: green;", // can be colored, like other named icons
});
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GtkWindow is not a layer surface

If Widget.Window shows as up as a regular window, it usually means ags is running in xwayland. Try running ags from a non xwayland terminal, or try

env GDK_BACKEND=wayland ags
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